Objective: Although clinical trials are needed to advance treatments for bipolar disorder, there has been little empirical research on the capacity of bipolar patients to consent to research. The aim of the present study was to evaluate levels of decisional capacity of bipolar patients compared with those of schizophrenia patients and healthy comparison subjects, as well as to examine whether symptom and neurocognitive deficits correlate with patients' decisional abilities.

Method: Participants were 31 outpatients with bipolar disorder, 31 outpatients with schizophrenia, and 28 healthy comparison subjects; each participant's decisional capacity was evaluated with the MacArthur Competence Assessment Tool for Clinical Research. Patient participants were also evaluated with standardized clinical rating scales and neurocognitive tests. Data were collected from April 2002 through November 2005.

Results: Bipolar patients had worse understanding than healthy comparison subjects, and their level of decisional capacity did not differ from that of schizophrenia patients. Within the combined patient sample, neurocognitive deficits and negative symptoms were significantly correlated (p < .05) with the level of decisional capacity (particularly, understanding of disclosed information). Repeating the missed information improved the level of understanding in all groups.

Conclusions: The presence of bipolar disorder appears to be a risk factor for impaired understanding of information disclosed under standard consent procedures but should not be equated with a lack of competence to consent. The observed improvement in understanding with redisclosure of information suggests that enhanced consent procedures may be useful during enrollment of bipolar patients in research.